Method of producing a COF flexible printed wiring board

ABSTRACT

The present invention provides a COF flexible printed wiring board whose insulating layer is not melt-adhered to a heating tool, to thereby enhance reliability and productivity of a semiconductor chip mounting line, and also provides a method of producing the COF flexible printed wiring board. The COF flexible printed wiring board contains an insulating layer, a wiring pattern, on which a semiconductor chip being mounted, formed of a conductor layer provided on at least one side of the insulating layer and a releasing layer, wherein the releasing layer is formed from a releasing agent containing at least one species selected from a silane compound and silica sol and is provided on a surface of the insulating layer, which is opposite to the mounting side of the semiconductor chip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of application Ser. No. 10/386,116 filed Mar. 12,2003, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a COF (chip-on-film) flexible printedwiring board; e.g., a COF film carrier tape or a COF flexible printedcircuit (FPC), for mounting electronic devices such as ICs and LSIsthereon. The invention also relates to a method of producing the COFflexible printed wiring board. The term “COF flexible printed wiringboard” refers to a flexible printed wiring board onto which electronicdevices (chips) are to be mounted. The term “COF film carrier tape”refers to a film substrate assuming the form of tape onto whichelectronic devices (chips) are to be mounted.

2. Description of the Related Art

Development of the electronics industry has been accompanied by sharpdemand for printed-circuit boards for mounting electronic devicesthereon, such as ICs (Integrated Circuits) and LSIs (Large-ScaleIntegrated circuits). Manufacturers have attempted to realizesmall-size, lightweight, and high-function electronic equipment, whichhas long been desired. To this end, manufactures have recently come toemploy a film carrier tape, such as a TAB (tape automated bonding) tape,a T-BGA (ball grid array) tape, an ASIC tape, or an FPC (flexibleprinted circuit). Use of film carrier tapes for mounting electronicdevices thereon has become of increasing importance, especially formanufacturers of personal computers, cellular phones, and otherelectronic equipment employing a liquid crystal display (LCD) that musthave high resolution and flatness, as well as a narrow screen-framearea.

In addition, in order to attain higher-density mounting on a narrowerspace, mounting of bare IC chips directly on a flexible printed wiringboard has been employed. Such a product is called COF (chip-on-film).

Since the flexible printed wiring board serving as a substrate of COFsdoes not have a device hole, a laminate film obtained by laminating inadvance a conductor layer and an insulating layer is employed as theflexible printed wiring board. When IC chips are directly mounted on thewiring pattern, positioning is performed on the basis of marks such asan inner lead and a positioning mark which are visible through theinsulating layer, followed by joining the IC chips and the wiringpattern; i.e., the inner lead, by means of a heating tool (see, forexample, Japanese Patent Application Laid-Open (kokai) No. 2002-289651,FIGS. 4 to 6 and paragraphs [0004] and [0005]).

Such semiconductor chips are mounted while the insulating layer is indirect contact with a heating tool. Since the insulating layer is heatedto a considerably high temperature by the heating tool during mounting,a portion of the insulating layer is caused to adhere to the heatingtool by melting, thereby causing stoppage of a production apparatus. Inaddition, unfavorable deformation of the carrier tape occurs. In thecase where the insulating layer is melt-adhered to the heating tool, theheating tool is stained, thereby deteriorating reliability andproductivity.

Such melt adhesion to the heating tool is critical when semiconductorchips are mounted on a COF film carrier tape or a COF FPC having nodevice hole.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a COF flexible printed wiring board whose insulating layer isnot melt-adhered to a heating tool, to thereby enhance reliability andproductivity of a semiconductor chip mounting line. Another object ofthe invention is to provide a method of producing the COF flexibleprinted wiring board.

Accordingly, in a first aspect of the present invention, there isprovided a COF flexible printed wiring board comprising: an insulatinglayer; a wiring pattern, on which a semiconductor chip being to bemounted, formed of a conductor layer provided on at least one side ofthe insulating layer and a releasing layer, wherein the releasing layeris formed from a releasing agent containing at least one speciesselected from a silane compound and silica sol and is provided on asurface of the insulating layer, which is opposite to the mounting sideof the semiconductor chip.

Through employment of the COF flexible printed wiring board according tothe first aspect, the releasing layer is brought into direct contactwith a heating tool during mounting of semiconductor chips. Thus, meltadhesion between the layer and the heating tool does not occur, therebypreventing staining of the heating tool caused by melt adhesion of theinsulating layer.

In the second aspect of the present invention, the releasing layer maybe formed from a releasing agent containing a silazane compound.

Through employment of the above construction according to the secondaspect, the releasing layer is formed from a silicone series releasingcontaining a silazane compound (i.e., a type of silane compound), meltadhesion can be reliably prevented.

In the third aspect of the present invention, the releasing layer may beformed by coating a solution containing the releasing agent to theinsulating layer and heating.

Through employment of the above construction according to the thirdaspect, the above releasing layer is formed through the coating method,melt adhesion can be reliably prevented.

In the forth aspect of the present invention, the releasing layer may beformed by transferring the releasing layer provided on a transfer filmsubstrate.

Through employment of the above construction according to the forthaspect, the above releasing layer can be readily formed through thetransfer method.

In the fifth aspect of the present invention, the insulating layer maybe formed by coating a solution containing a polyimide precursor resinto the conductor layer, drying the solution, and curing the resin.

Through employment of the above construction according to the fifthaspect, the insulating layer is formed in the above manner, a COFflexible printed wiring board having an insulating layer formed ofpolyimide can be obtained.

In the sixth aspect of the present invention, the insulating layer maycomprise a layer structure including an insulating film and athermoplastic resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to the sixthaspect, the insulating layer is formed, on the conductor layer, from athermoplastic resin layer and an insulating film.

In the seventh aspect of the present invention, the insulating layer maycomprise a layer structure including an insulating film and athermosetting resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to the seventhaspect, the insulating layer is formed, on the conductor layer, from athermosetting resin layer and an insulating film.

In the eighth aspect of the present invention, the conductor layer maycomprise a bond-improving layer sputtered on the insulating layer, and acopper plating layer provided on the bond-improving layer.

Through employment of this procedure according to the eighth aspect, theconductor layer is formed, on the insulating layer, from abond-improving layer (e.g., nickel) and a copper plating layer.

In the ninth aspect of the present invention, there is provided a methodof producing a COF flexible printed wiring board including an insulatinglayer and a wiring pattern, on which a semiconductor chip being to bemounted, formed through photolithography of a conductor layer providedon at least one side of the insulating layer, comprising: patterning theconductor layer through photolithography, to thereby form the wiringpattern; and, subsequently, forming a releasing layer on a surface ofthe insulating layer, which surface is opposite to the mounting side ofthe semiconductor chip.

Through employment of the method of producing a COF flexible printedwiring board according to the ninth aspect, the releasing layer, whichis firmly formed after completion of photolithography, is brought intocontact with a heating tool during mounting of semiconductor chips.Thus, adhesion of the releasing layer to the heating tool does notoccur, thereby preventing staining of the heating tool caused by meltadhesion of the insulating layer.

In the tenth aspect of the present invention, the releasing layer maycomprise a silicone series compound.

Through employment of the method according to the tenth aspect, thereleasing agent, which is to be in contact with a heating tool, is asilicone series releasing agent, melt adhesion or a similar phenomenoncan be reliably prevented.

In the eleventh aspect of the present invention, the releasing layer maybe formed from a releasing agent containing at least one speciesselected from among a siloxane compound, a silane compound, and a silicasol.

Through employment of the method according to the eleventh aspect, thereleasing layer, which is to be in contact with a heating tool, isformed from a releasing agent comprising a siloxane compound, a silanecompound, or silica sol, melt adhesion or a similar phenomenon can bereliably prevented.

In the twelfth aspect of the present invention, the formation of areleasing layer may comprise coating a solution containing a releasingagent and heating.

Through employment of this procedure according to the twelfth aspect,the releasing layer is formed by coating the releasing agent andoptionally heating.

In the thirteenth aspect of the present invention, the formation of areleasing layer may be performed at any timing after removal of a resistmask employed for forming the wiring pattern.

Through employment of this procedure according to the thirteenth aspect,the releasing layer is formed after the photolithographic process. Thus,the releasing layer is not dissolved by a photoresist remover or similarliquid, thereby attaining an effective releasing effect.

In the fourteenth aspect of the present invention, the insulating layermay be formed by coating a solution containing a polyimide precursorresin to the conductor layer, drying the solution, and curing the resin.

Through employment of the above embodiment according to the fourteenthaspect, a COF flexible printed wiring board having an insulating layerformed of polyimide can be provided.

In the fifteenth aspect of the present invention, the insulating layermay comprise a layer structure including an insulating film and athermoplastic resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to the fifteenthaspect, the insulating layer is formed, on the conductor layer, from athermoplastic resin layer and an insulating film.

In the sixteenth aspect of the present invention, the insulating layermay comprise a layer structure including an insulating film and athermosetting resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to the sixteenthaspect, the insulating layer is formed, on the conductor layer, from athermosetting resin layer and an insulating film.

In the seventeenth aspect of the present invention, the conductor layermay comprise a bond-improving layer sputtered on the insulating layer,and a copper plating layer provided on the bond-improving layer.

Through employment of the above embodiment according to the seventeenthaspect, the conductor layer is formed, on the insulating layer, from abond-improving layer (e.g., nickel) and a copper plating layer.

In the eighteenth aspect of the present invention, there is provided amethod of producing a COF flexible printed wiring board including ainsulating layer and a wiring pattern, on which a semiconductor chipbeing to be mounted, formed of a conductor layer provided on at leastone side of the insulating layer comprising: patterning the conductorlayer, to thereby form the wiring pattern; and transferring thereleasing layer formed on a film substrate for transferring to a surfaceof the insulating layer, which surface is opposite to the mounting sideof the semiconductor chip.

Through employment of the method of producing a COF flexible printedwiring board according to the eighteenth aspect, the releasing layer iscomparatively readily formed through the transfer process and is broughtinto contact with a heating tool during mounting of semiconductor chips.Thus, adhesion of the releasing layer to the heating tool or stage doesnot occur, thereby preventing staining of the heating tool caused bymelt adhesion of the insulating layer.

In the nineteenth aspect of the present invention, the releasing layermay comprise a silicone series compound.

Through employment of the method according to the nineteenth aspect,after the releasing layer, which is to be in contact with a heatingtool, comprises a silicone series compound, melt adhesion or a similarphenomenon can be reliably prevented.

In the twentieth aspect of the present invention, the releasing layermay be formed from a releasing agent containing at least one speciesselected from among a siloxane compound, a silane compound, and silicasol.

Through employment of the method according to the twentieth aspect, thereleasing layer, which is to be in contact with a heating tool, isformed from a releasing containing a siloxane compound, a silanecompound, or silica sol, melt adhesion or a similar phenomenon can bereliably prevented.

In the twenty-first aspect of the present invention, the insulatinglayer may be formed by coating a solution containing a polyimideprecursor resin to the conductor layer, drying the solution, and curingthe resin.

Through employment of the above embodiment according to the twenty-firstaspect, a COF flexible printed wiring board having an insulating layerformed of polyimide can be provided.

In the twenty-second aspect of the present invention, the insulatinglayer may comprise a layer structure including an insulating film and athermoplastic resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to thetwenty-second aspect, the insulating layer is formed, on the conductorlayer, from a thermoplastic resin layer and an insulating film.

In the twenty-third aspect of the present invention, the insulatinglayer may have a layer structure including an insulating film and athermosetting resin layer, wherein the structure is hot-press-adhered tothe conductor layer.

Through employment of the above embodiment according to the twenty-thirdaspect, the insulating layer is formed, on the conductor layer, from athermosetting resin layer and an insulating film.

In the twenty-forth aspect of the present invention, the conductor layermay comprise a bond-improving layer sputtered on the insulating layer,and a copper plating layer provided on the bond-improving layer.

Through employment of the method according to the twenty-forth aspect,the copper plating layer which is provided on the insulating layerserves as a conductor layer.

As described hereinabove, the COF flexible printed wiring board (e.g.,COF film carrier tape or COF FPC) of the present invention has aspecific silicone series releasing layer. Therefore, melt adhesion ofthe insulating layer of the film carrier tape to a heating tool isprevented during mounting of semiconductor chips, to thereby enhancereliability and productivity of a semiconductor chip mounting line.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood with reference to the following detailed descriptionof the preferred embodiments when considered in connection withaccompanying drawings, in which:

FIG. 1A is a schematic plan view of a COF film carrier tape according toone embodiment of the present invention;

FIG. 1B is a cross-sectional view of the COF film carrier tape accordingto the same embodiment of the present invention;

FIGS. 2A to 2G are cross-sectional views showing a method of producing aCOF film carrier tape according to one embodiment of the presentinvention;

FIGS. 3A to 3E are cross-sectional views showing a laminate film forproducing a COF according to another embodiment of the presentinvention; and

FIG. 4 is a cross-sectional view showing a method of producing a printedcircuit board according to one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The COF flexible printed wiring board (e.g., a COF film carrier tape ora COF FPC) of the present invention comprises a conductor layer and aninsulating layer. No particular limitation is imposed on the laminatefilm comprising a conductor layer and an insulating layer and used inthe COF flexible printed wiring board, and any type ofconductor-insulator laminate film can be employed. Examples of suchlaminate film include a laminate film prepared by sputtering abond-improving layer (e.g., Ni) on an insulating film (e.g., polyimidefilm) and plating copper on the bond-improving layer; a casting-typelaminate film prepared by coating polyimide to copper foil; and alaminate film prepared through hot-press-adhesion of an insulating filmonto copper foil through a thermoplastic or thermosetting resin.

The COF flexible printed wiring board of the present invention or theCOF flexible printed wiring board produced through the method of thepresent invention comprises the aforementioned laminate film and areleasing layer which is provided on the insulating layer of thelaminate film opposing the conductor layer. In the production method ofthe present invention, no particular limitation is imposed on thematerial for forming the releasing layer, so long as the material hassuch releasability that adhesion of the laminate film to a heating toolduring mounting of semiconductor chips is prevented and does not inducemelt adhesion by heat. Both inorganic and organic materials areemployable. Examples of preferred releasing agents include a siliconeseries releasing agent, an epoxy series releasing agent, or afluorine-containing compound, more preferably a silicone seriescompound; i.e., a compound having a siloxane bond (Si—O—Si). A releasinglayer comprising a silicone series compound is preferred, since thelayer can be formed in a relatively simple manner and does not tend toadversely affect adhesion of mold resin even when the releasing layer istransferred to a mount side of the produced printed circuit board.

Examples of the releasing agents for forming a releasing layercomprising a silicone series compound; i.e., a compound having asiloxane bond, include silicone series releasing agents.

More specifically, such releasing agents contain at least one speciesselected from among siloxane compounds such as disiloxane andtrisiloxane. Preferably, the releasing agent comprises a compound whichtransforms into a silicone series compound through application andreaction of the releasing agent. Examples of such compounds includesilane compounds such as monosilane, disilane, and trisilane; and silicasol series compounds.

Examples of more preferred releasing agents include releasing agentcontaining an alkoxysilane compound, or a silazane compound such ashexamethyldisilazane or perhydropolysilazane, which belongs to silanecompounds having a Si—NH—Si structure serving as a precursor for forminga siloxane bond. These releasing agents form a releasing layercomprising a compound having a siloxane bond through application thereofor reaction with moisture or a similar substance contained in air afterthe application. However, for example, in case silazane compound isused, unreacted Si—NH—Si may also be present in the releasing layer.

As described above, the most preferred releasing layer is formed of thesilicone series compound formed by reaction after the application.

Although the above releasing agents generally contain an organicsolvent, similar releasing agents of aqueous solution type or emulsionform may also be employed.

Specific examples of the releasing agents include silicone series resinSR 2411 (trade name: product of Dow Corning Toray Silicone Co., Ltd.,containing dimethylsiloxane-series silicone series oil, methyltri(methylethyl ketoxime)silane, toluene, and ligroin); silicone series resinSEPA-COAT (trade name: product of Shin-Etsu Chemical Co., Ltd.,containing silazane, synthetic isoparaffin, and ethyl acetate); andCOLCOAT SP-2014S (trade name: product of Colcoat Co., Ltd., containing asilane compound). Examples of releasing agents containing silica solinclude COLCOAT P and COLCOAT N-103X (trade names: products of ColcoatCo., Ltd.). A grain size of silica contained in silica sol is, forexample, 50 to 80 Å (angstrom).

Notably, provision of a releasing layer formed of a silicone seriesreleasing agent containing a silazane compound is particularlypreferred, since the releasing agent has excellent releasability forpreventing adhesion of the laminate film to a heating tool duringmounting of semiconductor chips and does not induce melt adhesion byheat. Examples of such releasing agents containing a silazane compoundinclude silicone series resin SEPA-COAT (trade name: product ofShin-Etsu Chemical Co., Ltd., containing silazane, syntheticisoparaffin, and ethyl acetate).

No particular limitation is imposed on the method for forming such areleasing layer, and any known method can be employed. For example, areleasing agent or a liquid thereof may be applied to a substratethrough spraying, dipping, or roller-coating. Alternatively, a releasinglayer provided on a transfer film may be transferred. In any case,bonding between the insulating layer and the releasing layer may beenhanced through, for example, heat treatment in order to preventpeeling of the releasing layer from the insulating layer. The releasinglayer is not necessarily provided uniformly on the entire insulatinglayer, and may be provided in the form of discontinuous islands. Forexample, in case the releasing layer is provided by transferring, incase the releasing layer may be provided on only the region between tworows of sprocket holes, which will be described later, or on the regioncorresponding to the region where semiconductor chips (IC) are to bemounted in a continued form or in the form of discontinuous islands. Noparticular limitation is imposed on the timing of provision of thereleasing layer, so long as the layer is provided prior to mounting ofsemiconductor elements. Specifically, the releasing layer may beprovided after provision of the conductor layer; provided in advance onan insulating layer which has not been provided with a conductor layer;or provided simultaneously with provision of the conductor layer.Needless to say, the releasing layer is not necessarily provided priorto patterning of the conductor layer, but may be provided afterpatterning of the conductor layer.

The transfer method is preferably employed in the cases in which, forexample, the releasing layer is provided after provision of theconductor layer or in advance on an insulating layer which has not beenprovided with a conductor layer. When the releasing layer is providedafter patterning of the conductor layer, the application method ispreferably employed. Needless to say, the timing of formation of thereleasing layer is not limited, and the layer may be provided at aninitial stage before patterning of the conductor layer throughapplication or may be provided after patterning of the conductor layerthrough transfer.

In one embodiment of the production method of the present invention, thereleasing layer is provided after the photolithographic process(pattering process) and before mounting of semiconductor elements. Thereason for choosing the above timing is that the releasing layer ispossibly dissolved by a photoresist remover or a similar material.Therefore, the releasing layer is preferably provided after etching ofthe conductor layer for removal of a resist mask for forming a wiringpattern. Specifically, the releasing layer is preferably provided, forexample, after formation of a tin plating layer preceded by removal of aresist mask or after plating of a lead electrode preceded by removal ofthe resist mask and provision of a solder resist layer. Such a releasinglayer may be formed by coating a solution containing a releasing agentand bringing the applied solution to dryness. However, in order toenhance bonding strength between the insulating layer and the releasinglayer, the applied solution is preferably heated. The conditions underwhich the heating is performed are, for example, at 50 to 200° C.,preferably 100 to 200° C. for one minute to 120 minutes, preferably 30minutes to 120 minutes.

According to another embodiment of the method of the present invention,a releasing layer provided on a transfer film may be transferred on asurface of the insulating layer, which surface is opposite to themounting side of the semiconductor chips (IC). Exemplary conditionsunder which the transfer is performed are, but are not limited to, aheating temperature of 15 to 200° C., a load for rolling or pressing of5 to 50 kg/cm², and a treatment time of 0.1 seconds to two hours.Bonding between the insulating layer and the releasing layer may beenhanced through, for example, heat treatment in order to preventpeeling of the releasing layer from the insulating layer. Exemplaryconditions under which the heating is performed are, but are not limitedto, at 50 to 200° C., preferably 100 to 200° C., preferably for oneminute to 120 minutes, preferably 30 minutes to 120 minutes.

According to the above transfer method, no particular limitation isimposed on the timing of provision of the releasing layer, so long asthe layer is provided prior to mounting of semiconductor elements.Specifically, the releasing layer may be provided in advance on aninsulating layer which has not been provided with a conductor layer; orprovided simultaneously with provision of the conductor layer. Needlessto say, the releasing layer is, not necessarily provided prior topatterning of the conductor layer, but may be provided after patterningof the conductor layer.

The transfer method is preferably employed in the cases in which, forexample, the releasing layer is provided in advance on an insulatinglayer which has not been provided with a conductor layer. In the case inwhich the releasing layer is provided through the transfer method at aninitial stage of production of the COF flexible printed wiring board,the following procedure may be employed. Specifically, the filmsubstrate is not peeled from the releasing layer, so as to serve as areinforcing film, and the film substrate is removed at a finalproduction step.

In use of the COF flexible printed wiring board of the presentinvention, a semiconductor chip is mounted thereon. No particularlimitation is imposed on the mounting method. For example, semiconductorchips are mounted by positioning and disposing the COF flexible printedwiring board on semiconductor chips which are placed on a chip stage,and pressing a heating tool against the COF flexible printed wiringboard. In this case, the heating tool is heated to at least 200° C., orin some cases, 350° C. or higher. However, since the COF flexibleprinted wiring board has a releasing layer formed on the insulatinglayer, melt adhesion between the heating tool and the insulating layercan be prevented.

Hereafter, a COF film carrier tape, which is one embodiment of the COFflexible printed wiring board of the present invention, will bedescribed with reference to FIGS. 1A and 1B. The following embodimentsof the present invention will be described taking a COF film carriertape as an example. However, needless to say, those with ordinary skillin the art would readily understand that COF FPCs can also be realizedin an analogous manner.

FIGS. 1A and 1B show a COF film carrier tape 20 according to oneembodiment of the present invention.

As shown in FIGS. 1A and 1B, the COF film carrier tape 20 according tothe present embodiment is formed from a laminate film 10 for producing aCOF, the laminate film comprising a conductor layer 11 (copper foil) andan insulating layer 12 (polyimide film). The COF film carrier tape 20has wiring patterns 21 obtained by patterning the conductor layer 11,and a pair of transversely spaced rows of sprocket holes 22 providedalong opposite longitudinal edges; this is, the two rows of sprocketholes 22 are disposed such that one row extends along each of theopposite longitudinal edges of the wiring pattern 21. The wiringpatterns 21 are provided on a surface of the insulating layer 12continuously in the longitudinal direction of the film carrier tape.Each wiring pattern 21 has, on a surface thereof, a solder resist layer23 which is formed by coating a solder resist coating solution throughscreen printing. Moreover, the wiring pattern may be formed on two sidesof the insulating layer (2-metal COF film carrier tape). In this case,the releasing layer may be formed on only the region where the heatingtool is to contact, by coating or transferring.

Although the conductor layer 11 can be formed from a metal other thancopper; e.g., aluminum, gold or silver, a copper layer is generallyemployed. No particular limitation is imposed on the type of copperlayer, and any type of copper layers, such as a copper layer formedthrough vapor deposition or plating, electrolyzed copper foil, or rolledcopper foil, can be used. Generally, the conductor layer 11 has athickness of 1 to 70 μm, preferably 5 to 35 μm.

The insulating layer 12 may be formed from, other than polyimide, apolymeric material such as polyester, polyamide, polyether-sulfone, orliquid crystalline polymer. Of these, an aromatic polyimide (allrepeating units being aromatic) prepared by polymerizing pyromelliticdianhydride and 4, 4′-diaminodiphenyl ether is preferred. The thicknessof the insulating layer 12 generally falls within a range of 12.5 to 125μm, preferably 12.5 to 75 μm, more preferably 12.5 to 50 μm.

The laminate film 10 for producing a COF is produced by, for example,coating to a conductor layer 11 (copper foil) a polyimide precursorresin composition containing a polyimide precursor and varnish, tothereby form a coating layer 12 a; removing the solvent by drying;winding the coating layer; and heating the wound coating layer in anoxygen-purged curing furnace for imidization, to thereby form theinsulating layer 12. However, no particular limitation is imposed on themethod for producing the laminate film.

A releasing layer 13 can be formed from a silicone series releasingagent containing a silazane compound or a releasing agent containingsilica sol. Preferably, the releasing layer 13 is formed by providing areleasing agent on the insulating layer 12 through, for example, theapplication method, followed by heating to thereby attain strong bondingbetween the releasing layer 13 and the insulating layer 12. Thereleasing layer 13 has a thickness of, for example, 0.1 to 1 μm.

On the above-described COF film carrier tape of the present invention,chips or electronic devices are mounted. For example, while the tape orsubstrate is conveyed, semiconductor chips are mounted on the tape, orelectronic devices are mounted on a print substrate, to thereby yieldCOF products. Since the insulating layer 12 has a optical transmittanceof 50% or higher, the image of the wiring patterns 21 (e.g. an innerlead) can be recognized from the side of the insulating layer 12 bymeans of a CCD or a similar device. In addition, the wiring patterns ofsemiconductor chips and printed circuit boards to be mounted can berecognized. Thus, precise positioning of the wiring patterns withrespect to the insulating layer 12 can be performed through imageprocessing, thereby mounting electronic devices at high precision.

Next, one exemplary method of producing the aforementioned COF filmcarrier tape will be described with reference to FIGS. 2A to 2G.

As shown in FIG. 2A, a laminate film 10 for producing a COF is provided.As shown in FIG. 2B, sprocket holes 22 are formed, by punching or asimilar method, through a conductor layer 11 and an insulating layer 12.These sprocket holes 22 may be formed from the front side or thebackside of the insulating layer 12. Then, as shown in FIG. 2C, aphotoresist coating layer 30 is formed on a region of the conductorlayer 11 for providing a wiring pattern 21, through a routinephotolithographic method involving application of, for example, anegative type photoresist coating solution. Needless to say, a positivetype photoresist can also be employed. After the insulating layer 12 ispositioned by inserting positioning pins in the sprocket hole 22, thephotoresist coating layer 30 is exposed and developed via a photomask 31for patterning thereof, thereby forming a resist pattern 32 forproviding a wiring pattern as shown in FIG. 2D. Subsequently, theconductor layer 11 is removed by dissolving with an etchant through theresist pattern 32 serving as a mask pattern, and the resist pattern 32is removed by dissolving with an alkaline solution or a similarmaterial, thereby forming a wiring pattern 21 as shown in FIG. 2E.

Here, when the wiring pattern 21 is formed, a dummy wiring pattern,which is formed discontinuous with the wiring pattern 21, may be formedin such a manner that the sprocket holes 22 are surrounded. In thiscase, the dummy wiring pattern could reinforce the insulator layer 12,thereby enable to carry the insulator layer 12 certainly and well, whenthe COF film carrier tape are manufactured. The dummy wiring pattern maybe formed continuously along longitudinal direction of the insulatorlayer 12. The dummy wiring pattern may also be formed around each ofsprocket holes 22 discontinuously, thereby improving rigidity of theinsulator layer 12 in a manner which could be carried certainly.

The entirety of the thus-formed wiring pattern 21 is plated (e.g.,plated with tin) in accordance with needs, and then a releasing layer 13is formed, through the application method, on the insulating layer 12,as shown in FIG. 2F. Although the applied releasing layer 13 may besimply dried, heating of the layer is preferred, for enhancing areleasing effect; i.e., for preventing melt adhesion of a heating tooland the insulating layer. Exemplary conditions under which the heatingis performed are, but are not limited to, at 50 to 200° C., preferably100 to 200° C. for one minute to 120 minutes, preferably 30 minutes to120 minutes. Subsequently, a solder resist layer 23 is formed through,for example, screen printing, as shown in FIG. 2G. An outer lead and aninner lead, which are not covered with the solder resist layer 23, areplated with a metal in accordance with needs. No particular limitationis imposed on the material of the metal plating layer, and tin plating,tin alloy plating, nickel plating, gold plating, gold alloy plating,etc. may appropriately be performed in accordance with the purpose ofuse.

In the embodiment described above, the releasing layer 13 is formedafter removal of the resist pattern 32 with an alkali solution or asimilar material and before provision of the solder resist layer 23.Alternatively, the releasing layer 13 may be formed in the finalproduction step after provision of the solder resist layer 23. When thereleasing layer 13 is formed through the latter method, exposure of thereleasing layer 13 to an etchant, a photoresist remover, etc. isprevented, thereby attaining a high releasing effect. As describedhereinabove, the term “final production step” refers to as a stepimmediately before the product inspection step.

As described above, the releasing layer of the present invention ispreferably formed after the photolithography step for forming wiringpatterns 21 and before bonding with semiconductor chips. The reason forthe timing is that the releasing layer is possibly dissolved in aphotoresist layer removal step. Therefore, the releasing layer 13 ispreferably formed immediately after completion of the photolithographystep or after plating, more preferably after formation of the solderresist layer 23 or a similar step. Needless to say, the releasing layer13 may also be formed before the photolithography step.

The releasing layer may be formed through the transfer method.Specifically, the aforementioned COF film carrier tape may be producedfrom a laminate film 10A for producing a COF as shown in FIGS. 3A to 3E.The laminate film shown in FIGS. 3A to 3E is produced by coating to aconductor layer 11 (copper foil, FIG. 3A) a polyimide precursor resincomposition containing a polyimide precursor and varnish, to therebyform a coating layer 12 a (FIG. 3B); removing the solvent by drying;winding the coating layer; and heating the wound coating layer in acuring furnace for imidization, to thereby form the insulating layer 12(FIG. 3C). Subsequently, a releasing layer 13 a formed on a transferfilm 14 serving as a transfer substrate is brought into firm contactwith the surface of the insulating layer 12 opposite to the side of theconductor layer 11 (FIG. 3D) and heated. Then, the transfer film 14 ispeeled, thereby forming the laminate film 10A for producing a COF andhaving a releasing layer 13A (FIG. 3E). Exemplary conditions under whichthe transfer is performed are, but are not limited to, a heatingtemperature of 15 to 200° C., a load for rolling or pressing of 5 to 50kg/cm², and a treatment time of 0.1 seconds to two hours. Exemplaryconditions under which the heating is performed are, but are not limitedto, at 50 to 200° C., preferably 100 to 200° C. for one minute to 120minutes, preferably 30 minutes to 120 minutes. Needless to say,formation of the releasing layer 13A through transfer may be performedafter the photolithography step or a similar step. Examples of thematerial of the transfer film 14 include PET (polyethyleneterephthalate), PI (polyimide), and liquid crystal polymers. Thethickness of such transfer film 14 is, for example, 15 to 100 μm,preferably 20 to 75 μm.

As shown in FIG. 4, the printed circuit board of the present inventionis produced by mounting a semiconductor chip 30 on a COF film carriertape 20 produced in the above-described manner. Specifically, the COFfilm carrier tape 20 is conveyed and then positioned at a predeterminedposition, while the semiconductor chip 30 is placed on a chip stage 41.Subsequently, the COF film carrier tape 20 is fixed by means of upperclampers 42 and lower clampers 43, with each upper clamper 42 descendingwhile a corresponding lower clamper 43 ascending. A heating tool 45 ispressed against the thus-fixed COF film carrier tape 20 so as to heatthe tape, and further descends, thereby pressing an inner lead of thefilm carrier tape 20 against a bump 31 of the semiconductor chip 30.Pressing is performed for a predetermined period of time, therebybonding the inner lead and the semiconductor chip 30. After completionof bonding, the bonded chip is sealed with resin, to thereby produce aprinted circuit board.

Depending on time and pressure of pressing or other conditions, thetemperature of the heating tool 45 is controlled to 200° C. or higher,preferably 350° C. or higher. According to the present invention, evenwhen the heating tool 45 is heated to such high temperature, meltadhesion between the COF film carrier tape 20 and the heating tool 45 isprevented by virtue of a releasing layer 13 provided on a surface of thefilm carrier tape 20 to be brought into contact with the heating tool45. Therefore, according to the present invention, bonding can beperformed at sufficiently high temperature, thereby ensuring highbonding strength. In other words, since heating temperature can beelevated for attaining a predetermined level of bonding strength, thetime required for press bonding can be shortened, which is advantageous.

EXAMPLES

Examples 1a to 1d

A variety of commercially available polyimide film substrates; i.e.,S'PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.;Example 1a), ESPANEX (trade name: product of Nippon Steel Chemical Co.,Ltd.; Example 1b), NEOFLEX (trade name: product of Mitsui Chemicals,Inc.; Example 1c), and UPISEL (trade name: product of Ube Industries,Ltd.; Example 1d) were used to provide laminate films for producing aCOF. A conductor layer of each laminate film was patterned by use of aphotoresist. The entirety of the resultant pattern was tin-plated, and asilicone series resin (containing a silane compound), SR2411 (tradename: product of Dow Corning Toray Silicone Co., Ltd.), was applied tothe backside of the film substrate. The coating was heated at 125° C.for one hour, to thereby form a COF film carrier tape having a releasinglayer.

Examples 2a to 2d

A variety of commercially available polyimide film substrates similar tothose employed in Examples 1a to 1d; i.e., S'PERFLEX (trade name:product of Sumitomo Metal Mining Co., Ltd.; Example 2a), ESPANEX (tradename: product of Nippon Steel Chemical Co., Ltd.; Example 2b), NEOFLEX(trade name: product of Mitsui Chemicals, Inc.; Example 2c), and UPISEL(trade name: product of Ube Industries, Ltd.; Example 2d) were used toprovide laminate films for producing a COF. A conductor layer of eachlaminate film was patterned by use of a photoresist. The entirety of theresultant pattern was tin-plated, and a silicone series resin(containing silazane), SEPA-COAT (trade name: product of Shin-EtsuChemical Co., Ltd.), was applied to the backside of the film substrate.The coating was heated at 125° C. for one hour, to thereby form a COFfilm carrier tape having a releasing layer.

Comparative Examples 1a to 1d and 2a to 2d

The procedure of Examples 1a to 1d and 2a to 2d were repeated, exceptthat no releasing layer was provided, to thereby yield COF film carriertapes of Comparative Examples 1a to 1d and 2a to 2d, respectively.

Test Example 1

A heating tool was pressed against the releasing layer 13 of each of COFfilm carrier tapes produced in Examples 1a to 1d and 2a to 2d andComparative Examples 1a to 1d and 2a to 2d. The temperature of theheating tool was varied within a range of 260° C. to 440° C. Under theheating conditions, semiconductor chips were mounted. Adhesion betweenthe releasing layer and the heating tool was observed, and thetemperature at which adhesion occurred was determined. The results areshown in Table 1.

TABLE 1 Releasing Film Adhesion temperature (° C.) agent substrateExamples Comp. Exs. 1a SR2411 S'PERFLEX 370 320 1b SR2411 ESPANEX 360320 1c SR2411 NEOFLEX 360 340 1d SR2411 UPISEL 350 260 2a SEPA-COATS'PERFLEX 440 320 2b SEPA-COAT ESPANEX 390 320 2c SEPA-COAT NEOFLEX 400340 2d SEPA-COAT UPISEL 360 260

As is clear from Table 1, the film carrier tapes of Examples 1a to 1dand 2a to 2d exhibit remarkably high adhesion resistance (i.e., highreleasing effect), as compared with those of Comparative Examples 1a to1d and 2a to 2d having no releasing layer 13.

Examples 3a to 3d

A variety of commercially available polyimide film substrates similar tothose employed in Examples 1a to 1d; i.e., S'PERFLEX (trade name:product of Sumitomo Metal Mining Co., Ltd.; Example 3a), ESPANEX (tradename: product of Nippon Steel Chemical Co., Ltd.; Example 3b), NEOFLEX(trade name: product of Mitsui Chemicals, Inc.; Example 3c), and UPISEL(trade name: product of Ube Industries, Ltd.; Example 3d) were used toprovide laminate films for producing a COF. A conductor layer of eachlaminate film was patterned by use of a photolithographic process, tothereby form a wiring pattern. The entirety of the wiring pattern wastin-plated, and subsequently a silicone series oil, SRX310 (trade name:product of Dow Corning Toray Silicone Co., Ltd.), was applied to thebackside of the film substrate. The coating was heated at 125° C. forone hour, to thereby form a COF film carrier tape having a releasinglayer.

Comparative Examples 3a to 3d

The procedure of Examples 3a to 3d were repeated, except that noreleasing layer was provided, to thereby yield COF film carrier tapes ofComparative Examples 3a to 3d, respectively.

Test Example 2

A heating tool was pressed against the releasing layer 13 of each of COFfilm carrier tapes produced in Examples 3a to 3d and ComparativeExamples 3a to 3d. The temperature of the heating tool was varied withina range of 260° C. to 400° C. Under the heating conditions,semiconductor chips were mounted. Adhesion between the releasing layerand the heating tool was observed, and the temperature at which adhesionoccurred was determined. The results are shown in Table 2.

TABLE 2 Adhesion temperature (° C.) Examples Comp. Exs. 3a: S'PERFLEX400 320 3b: ESPANEX 350 320 3c: NEOFLEX 370 340 3d: UPISEL 280 260

As is clear from Table 2, the film carrier tapes of Examples 3a to 3cexhibit remarkably high adhesion resistance as compared with those ofComparative Examples 3a to 3c. Although the film carrier tape of Example3d exhibits an adhesion temperature higher than that of the film carriertape of Comparative Example 3d, the difference in temperature wascomparatively small. However, in view that the temperature at whichsemiconductor elements are mounted through melt adhesion variesdepending on the type of heating tools, the type of semiconductor chips,use of the element-mounted products, etc., and is generally about 200°C. to about 350° C., such a small increase in adhesion temperature wouldsuffice for purposes of the present invention.

Examples 4a to 4h

The procedure of Example 1a was repeated, except that the timing ofapplication of SEPA-COAT (trade name: product of Shin-Etsu Chemical Co.,Ltd.) was varied, to thereby produce COF film carrier tapes.Specifically, the releasing layer was obtained by coating SEPA-COAT to alaminate film for producing a COF, followed by air-drying for threehours or longer (Example 4a); by heating the applied SEPA-COAT at 125°C. for one hour instead of air-drying (Example 4b); by coating SEPA-COATat a cleaning step performed before patterning of the conductor layer,followed by air-drying for three hours or longer (Example 4c); byheating the thus-applied SEPA-COAT at 125° C. for one hour instead ofair-drying (Example 4d); by coating SEPA-COAT after development of aphotoresist for patterning the conductor layer, followed by air-dryingfor three hours or longer (Example 4e); by heating the thus-appliedSEPA-COAT at 125° C. for one hour instead of air-drying (Example 4f); bycoating SEPA-COAT after patterning of the conductor layer, removal ofphotoresist, and plating of tin, followed by air-drying for three hoursor longer (Example 4g); or by heating the thus-applied SEPA-COAT at 125°C. for one hour instead of air-drying (Example 4h).

Test Example 3

A heating tool was pressed against the releasing layer 13 of each of COFfilm carrier tapes produced in Examples 4a to 4h. The temperature of theheating tool was varied within a range of 340° C. to 490° C. Under theheating conditions, semiconductor chips were mounted. Adhesion betweenthe releasing layer and the heating tool was observed, and thetemperature at which adhesion occurred was determined. The results areshown in Table 3.

TABLE 3 Adhesion temperature (° C.) Example 4a 350 Example 4b 360Example 4c 350 Example 4d 370 Example 4e 340 Example 4f 380 Example 4g480 Example 4h 490

As is clear from Table 3, the film carrier tapes of Examples 4g and 4h,in which the releasing layer is formed after removal of photoresist,exhibit excellent adhesion resistance. A possible reason for excellentadhesion resistance is that the releasing layer is partially dissolvedupon removal of photoresist performed after the photolithography step.As is also clear from the results, in the case in which the releasinglayer is provided through the application method, adhesion resistance isfurther enhanced by heat treatment, as compared with air-drying withoutany additional heat treatment.

Examples 5a to 5e

In a manner similar to that for producing the film carrier tapes ofExamples 4a to 4h, patterning of the conductor layer, removal ofphotoresist, plating with tin, and application of a silicone seriesresin were performed, to thereby produce film carrier tapes. Formationof the releasing layer was performed by air-drying three hours or longeror heating for one hour at 125° C. In Examples 5a to 5e, the siliconeseries resin, SEPA-COAT (trade name: product of Shin-Etsu Chemical Co.,Ltd.), was diluted with ethyl acetate at a variety of dilution factors:i.e., 1 (undiluted), 2, 3, 5, and 10 times. In each case, the thicknessof the releasing layer was calculated.

Test Example 4

A heating tool was pressed against the releasing layer 13 of each of COFfilm carrier tapes produced in Examples 5a to 5e. The temperature of theheating tool was varied within a range of 320° C. to 460° C. Under theheating conditions, semiconductor chips were mounted. Adhesion betweenthe releasing layer and the heating tool was observed, and thetemperature at which adhesion occurred was determined. The results areshown in Table 4.

TABLE 4 Adhesion Layer thickness temperature (° C.) (μm) Non-heatedHeated Example 5a 0.35 440 460 Example 5b 0.18 440 440 Example 5c 0.12400 410 Example 5d 0.07 370 390 Example 5e 0.04 320 320

As is clear from Table 4, the film carrier tapes having a releasinglayer thickness 0.05 μm or more exhibit adhesion resistance. Asconfirmed with Examples 5a to 5c, the film carrier tapes having areleasing layer thickness in excess of 0.1 μm exhibit remarkably highadhesion resistance.

Example 6

A polyimide layer (thickness: 40 μm) serving as an insulating layer 12was formed through the application method on copper foil (thickness: 9μm) of ultra-minute roughness serving as a conductor 11. On the othersurface (opposite to the conductor 11) of the copper foil, a releasinglayer 13 (thickness: 0.1 μm) formed of a silicone series compound wasprovided through the transfer method, thereby yielding a COF filmcarrier tape of Example 6. After completion of transferring of thereleasing layer 13 formed from the silicone series compound, the filmcarrier tape was heated at 120° C.

Example 7

The procedure of Example 6 was repeated, except that heating treatmentto be performed after transfer of the silicone series releasing agentwas omitted, to thereby yield a laminate film for producing a COF ofExample 7.

Example 8

The procedure of Example 6 was repeated, except that the silicone seriescompound the releasing layer 13 formed through transfer method waschanged to formed from SEPA-COAT (trade name: product of Shin-EtsuChemical Co., Ltd.), to thereby yield a laminate film for producing aCOF of Example 8.

Comparative Example 4

The procedure of Example 6 was repeated, except that provision of thereleasing layer 13 was omitted, to thereby yield a laminate film forproducing a COF of Comparative Example 4.

Test Example 5

The conductor 11 of each of COF film carrier tapes of Examples 6 to 8and Comparative Example 4 was patterned. A heating tool was pressedagainst the releasing layer 13 of each film carrier tape. Thetemperature of the heating tool was varied within a range of 260° C. to440° C. Under the heating conditions, semiconductor chips were mounted.Adhesion between the releasing layer and the heating tool was observed,and the temperature at which adhesion occurred was determined. Theresults are shown in Table 5.

TABLE 5 Tool temperature Comparative (° C.) Example 6 Example 7 Example8 Example 4 260 ∘ ∘ ∘ ∘ 280 ∘ ∘ ∘ ∘ 300 ∘ ∘ ∘ x 320 ∘ Δ ∘ x 340 ∘ Δ ∘ x360 ∘ x ∘ x 380 ∘ x ∘ x 400 ∘ x ∘ x 420 x x ∘ x 440 x x x x ∘: noadhesion, Δ: partially adhered, x: adhered

As is clear from Table 5, the film carrier tape of Comparative Example 4adhered to the heating tool when the temperature exceeds 300° C. Thefilm carrier tape of Example 7 exhibits such an excellent adhesionresistance that the tape partially adheres to the heating tool when thetemperature exceeds 320° C. The film carrier tapes of Examples 6 and 8cause no adhesion when the temperature is 400° C. or lower. Although thefilm carrier tape of Example 7 exhibits an adhesion temperature higherthan that of the film carrier tape of Comparative Example 4, thedifference in temperature was comparatively small. However, in view thatthe temperature at which semiconductor elements are mounted through meltadhesion varies depending on the type of heating tools, the type ofsemiconductor chips, use of the element-mounted products, etc., and isgenerally about 200° C. to about 350° C., such a small increase inadhesion temperature would suffice for purposes of the presentinvention.

Examples 9a to 9c

S'PERFLEX (trade name: product of Sumitomo Metal Mining Co., Ltd.) wasemployed as a film substrate, and, as a releasing agent, COLCOAT P(trade name: product of Colcoat Co., Ltd., silica sol-containing;Example 9a); COLCOAT N-103X (trade name: product of Colcoat Co., Ltd.;Example 9b); and COLCOAT SP-2014S (trade name: product of Colcoat Co.,Ltd., containing silane compound; Example 9c) were used. The entirety ofthe provided wiring pattern was tin-plated, and subsequently, eachreleasing agent was applied to the backside of the film substrate. Thecoating was dried by heating at 120° C. for 60 minutes, to thereby forma COF film carrier tape having a releasing layer.

Test Example 6

A heating tool was pressed against the releasing layer 13 of each of COFfilm carrier tapes produced in Examples 9a to 9c. The temperature of theheating tool was varied within a range of 440° C. to 480° C. Under theheating conditions, semiconductor chips were mounted, to thereby producea printed circuit board.

During production of printed circuit boards of Examples 9a to 9c,adhesion between the releasing layer and the heating tool was observed,and the temperature at which adhesion occurred was determined. Theresults are shown in Table 6.

TABLE 6 Examples Adhesion temperature (° C.) 9a: COLCOAT P 460 9b:COLCOAT N-103X 480 9c: COLCOAT SP-2014S 440

As is clear from Table 6, the film carrier tapes of Examples 9a to 9calso exhibit remarkably high adhesion resistance.

1. A method of producing a COF flexible printed wiring board includingan insulating layer and a wiring pattern, on which semiconductor chipsare to be mounted, formed through photolithography of a conductor layerprovided on at least one side of the insulating layer, comprising:patterning the conductor layer through photolithography to thereby formthe wiring pattern; and, subsequently, forming a releasing layer on asurface of the insulating layer, which surface is opposite to themounting side of semiconductor chips.
 2. A method of producing a COFflexible printed wiring board according to claim 1, wherein thereleasing layer comprises a silicone series compound.
 3. A method ofproducing a COF flexible printed wiring board according to claim 1,wherein the releasing layer is formed from a releasing agent containingat least one species selected from among a siloxane compound, a silanecompound, and silica sol.
 4. A method of producing a COF flexibleprinted wiring board according to claim 1, wherein the formation of areleasing layer comprises coating a solution containing a releasingagent and heating.
 5. A method of producing a COF flexible printedwiring board according to claim 1, wherein the formation of a releasinglayer is performed at any timing after removal of a resist mask employedfor forming the wiring pattern.
 6. A method of producing a COF flexibleprinted wiring board according to claim 1, wherein the insulating layeris formed by coating a solution containing a polyimide precursor resinto the conductor layer, drying the solution, and curing the resin.
 7. Amethod of producing a COF flexible printed wiring board according toclaim 1, wherein the insulating layer comprises a layer structureincluding an insulating film and a thermoplastic resin layer, whereinthe structure is hot-press-adhered to the conductor layer.
 8. A methodof producing a COF flexible printed wiring board according to claim 1,wherein the insulating layer comprises a layer structure including aninsulating film and a thermosetting resin layer, wherein the structureis hot-press-adhered to the conductor layer.
 9. A method of producing aCOF flexible printed wiring board according to claim 1, wherein theconductor layer comprises a bond-improving layer sputtered on theinsulating layer, and a copper plating layer provided on thebond-improving layer.
 10. A method of producing a COF flexible printedwiring board including an insulating layer and a wiring pattern, onwhich a semiconductor chip is to be mounted, formed of a conductor layerprovided on at least one side of the insulating layer comprising:patterning the conductor layer, to thereby form the wiring pattern; andsubsequently, transferring the releasing layer formed on a filmsubstrate for transferring, to a surface of the insulating layer, whichsurface is opposite to the mounting side of the semiconductor chip. 11.A method of producing a COF flexible printed wiring board according toclaim 10, wherein the releasing layer comprises a silicone seriescompound.
 12. A method of producing a COF flexible printed wiring boardaccording to claim 10, wherein the releasing layer is formed from areleasing agent containing at least one species selected from among asiloxane compound, a silane compound, and silica sol.
 13. A method ofproducing a COF flexible printed wiring board according to claim 10,wherein the insulating layer is formed by coating a solution containinga polyimide precursor resin to the conductor layer, drying the solution,and curing the resin.
 14. A method of producing a COF flexible printedwiring board according to claim 10, wherein the insulating layercomprises a layer structure including an insulating film and athermoplastic resin layer, wherein the structure is hot-press-adhered tothe conductor layer.
 15. A method of producing a COF flexible printedwiring board according to claim 10, wherein the insulating layercomprises a layer structure including an insulating film and athermosetting resin layer, wherein the structure is hot-press-adhered tothe conductor layer.
 16. A method of producing a COF flexible printedwiring board according to claim 10, wherein the conductor layercomprises a bond-improving layer sputtered on the insulating layer, anda copper plating layer provided on the bond-improving layer.